1. Field of the Invention
The present invention relates to a bag filling and packaging apparatus in which a plurality of grippers are moved continuously or intermittently along a racetrack-shaped annular track, and in the process of this movement of the grippers, packaging operations including, among others, supply of bags to the grippers, holding of the edges of bags by the grippers, opening of the bag mouth, filling of bags with product, and sealing of the bag mouth are performed.
2. Description of the Related Art
U.S. Pat. No. 4,509,313 discloses a bag filling and packaging apparatus, and this bag filling and packaging apparatus comprises an endless chain that continuously moves along a racetrack-shaped annular track and a plurality of pairs of grippers that are disposed at equal intervals along the length of the endless chain and are moved together with the endless chain, and it further includes a bag supply device, a bag mouth opening device, a filling device and a sealing device that are among others disposed along the annular track. The bag supply device and bag mouth opening device are disposed along one linear section of the annular track, while the filling device includes a plurality of ascending/descending hoppers that are disposed above one semicircular section of the annular track (the semicircular section being on the downstream side of the linear section) and are moved along their own circular track which is concentric to the arc-shaped section of the annular track; and further the sealing device is disposed along the other linear section of the annular track.
In this bag filling and packaging apparatus, during the process of the movement of the grippers, packaging operations are performed including supply of bags to the grippers by the bag supply device, holding of the edges of bags by the grippers, opening of the bag mouth by the bag mouth opening device, filling of bags with product via the hoppers by the filling device, and sealing of the bag mouth by the sealing device. The hoppers (and their bottom-end openings in particular) are disposed at equiangular intervals (the same equiangular intervals as between the grippers when the grippers are traveling upon the semicircular sections of the annular track), and they are thus moved in a rotary manner synchronized with the grippers while the grippers are rotating above the circular track along the semicircular sections of the annular track. During the period of this rotary motion, the hoppers drop down from a position directly above the bags held by the grippers (such position being a standby position) to a filling position (where a product is filled in the bags), their bottom-end openings are inserted into the mouths of the bags, the product is introduced into the hopper and then drops from the bottom-end openings into the bags, and the hoppers are then raised and their bottom-end openings are removed out from the mouths of the bags, and the hoppers return to the standby positions. The semicircular region of the circular track of the hoppers during which a product filling step takes place is called the “filling region,” while the other semicircular region where the circular track of the hoppers diverges from the annular track of the grippers (where the hoppers and grippers are not in synchronized rotary motion) is called the “non-filling region,” and in this non-filling region the hoppers are at the standby positions.
The bag filling and packaging apparatus described above is able to perform bag filling and packaging with high productivity; however, in cases in which the bottom-end openings of the hoppers are set to a relatively small size to match the size of the bag mouths, product can easily clog the hopper, and the apparatus has no means of detecting or clearing such clogging if it occurs.
In contrast, in the filling device disclosed in the Japanese Patent No. 3,342,262, a pair of alligator frames that are able to open and close along and an air cylinder that opens and closes the alligator frames are disposed at the bottom of the hopper, so that the bottom ends of the closed alligator frames are inserted into the bag mouth and then opened, thus introducing the product into the bag via the hopper and alligator frames. With this type of opening/closing alligator frame provided at the bottom of the hopper, there is no need to make the bottom-end opening of the hopper excessively small, and as a result, it is possible to prevent clogging of product inside the hopper; and also, by repeatedly opening and closing the alligator frames inserted in the bag mouths, the action of the product dropping into the bag is promoted, and it is thereby possible to prevent clogging of product in the alligator frame (even if temporary clogging occurs, it can be automatically cleared).
However, even if the technology of the Japanese Patent No. 3,342,262 were to be applied “as is” to a bag filling and packaging apparatus of the type presented in the U.S. Pat. No. 4,509,313, it is still not possible to take sufficient time to allow the alligator frames inserted in the bag mouth to open and close; and a problem arises in which if sufficient time is taken, then the original advantage of high productivity is degraded.
On the other hand, the Japanese Patent No. 2,745,203 discloses a method of detecting clogging in a hopper by means of detection sensors or the like that are disposed in the upper portion of the hopper. Though the Japanese Patent No. 2,745,203 does not recite what is to be done after hopper clogging is detected, in the case in which clogging of the hopper is detected, typically the operation of the packaging apparatus is immediately halted, so that the clogging is cleared manually, and the operation of the packaging apparatus is then restarted.
However, in the bag filling and packaging apparatus of the type disclosed in the U.S. Pat. No. 4,509,313, halting the operation of the packaging apparatus each time the clogging is detected in one of the plurality of hoppers would degrade the original advantage of high productivity.